This invention relates to a rafter to plate connection in wood frame construction.
In wood frame construction, the standard way to attach the lower end of a rafter to a top plate is to cut a "bird-mouth" in the rafter and toe nail the rafter to the top plate. Notching rafters by cutting a "birds mouth" weakens them, however, and requires skillful time consuming sawing. Toe nailing to the top plate provides little uplift resistance caused by hurricanes, typhoons, and earthquakes.
Metal connectors for attaching roof trusses to wood top plates are not new to the industry. Daniels U.S. Pat. No. 1,652,612, 1927 discloses a joist and beam coupling. Daniels does not provide a bearing seat for the bottom edge of the rafter. All the weight of the rafter rests on a pin inserted through a bore hole in the rafter and on the outer edge of the plate. Where roof loads are very high, the pin bearing provided by Daniels is inadequate and would result in splitting of the rafter.
Daniels U.S. Pat. No. 1,657,243, 1928 discloses a rafter bracket with a sloping bearing seat, but there is no adjustability provided for rafters of different slopes. Also, the bracket connects to the inside face of the wood top plate where it would interfere with the installation of gypsum board or joist hangers hung on the inside wall.
Huff, U.S. Pat. No. 2,354,801, 1944, discloses a sloping rafter seat, but provides no adjustability for attaching rafters at different pitches.
Barnett, U.S. Pat. No. 2,477,163, 1949, discloses a truss shoe which does not provide a sloping seat. The rafter must be cut on its bottom edge to fit into the bracket, and the end is cut off to prevent overhang. Tracy, U.S. Pat. No. 3,423,898, 1969, in FIG. 2 discloses a rafter bracket which does not have a sloping seat and must be attached to both the inside and outside of the top plate.
Snow, U.S. Pat. No. 3,967,908, 1976 discloses a bracket which does not have a sloping seat and further requires cutting or notching of the bottom edge of the rafter.
Gilb and Commins, U.S. Pat. No. 4,410,294, 1983 discloses a commercially available adjustable variable pitch connector with a variable sloping seat. The Gilb and Commins connector has two features which limit its use; viz. the connector attaches to the inside of the top plate which may interfere with the wall board or ceiling joist hangers which are attached below or closely adjacent the rafter connector and the connector is limited to a slope between 6/12 and 1/12.
Other commercially available rafter connectors which provide an adjustable sloping seat and are attached to the outside edge of the top plate have the following problems: 1) they are limited to a pitch of 6/12 to 1/12, 2.) provide minimal uplift resistance in the event of hurricanes, tornadoes and earthquakes, 3) they are expensive to make, and 4) require too much material in their construction.